Combustion control



July 15, 1941. J. J. KLlNKER COMBUSTION CONTROL Filed April 8, 1939 JOHN J. KLINKER wow,

Patented July 15, 1941 Pica I COMBUSTION CONTROL John J.- Klinker, Decatur, Ill., assignor to A. W. Cash Company, Decatur, 111., a corporation of Delaware Application April 8, 1939, Serial No. 266,773

5Claims. (01. 236-44) This invention relates to combustion control,

and more particularly to the control of combustion in furnaces having a fuel bed through which air is caused to flow solely by maintenance of a sub-atmospheric pressure at the furnace outlet. This sub-atmospheric pressure may be produced either by a stack (natural draft), or'by a'fan or its equivalent (induced draft).

In furnaces of this type the rate of combustion is determined by the rate of air flow through the fuel bed, but this air flow 'is' dependent'upon several variables, including the draft available and the thickness and character of the fuel bed. Thus it is difficult to maintain any desired con stant rate of combustion. The problem is even more serious in installations having a plurality of furnaces among which the load is divided, for if the fuel bed on one furnace becomes thinthis furnace will operate at a higher combustion rate than the others, and the fuel bed will tend to become even thinner, a-ccentuating the unbalanced conditions. Variations in the distribution of the draft among the respective furnaces will cause similar difficulties;

It is accordingly one object of the invention to provide a simple and inexpensive method and apparatus for controlling combustion in furnaces of the aforesaid type and for maintaining the rate of combustion at a desired value.

It is a further object of the invention to provide a simple and inexpensive method and apparatus for controlling combustion and ensuring a desired distribution of the load among a plurality of furnaces of the aforesaid type. With these and other objects in view, as will be apparent to those skilled in the art, theinvention resides in the combination of parts and the steps of the process set forth in the specification and covered by the claimsappended hereto.

Referring to the drawing illustrating one 'embodiment of the invention and in which like reference numerals indicate like parts, the single figure is a front elevation of a pair of steam boiler furnaces and associated combustioncontrol apparatus, certain parts being broken away for clearness of illustration. r

The embodiment illustrated comprises a pair of furnaces set in battery and eachhaving a grate H to which fuel may be supplied manually through the usual fire-doors -l2. Associated with each furnace is a steam boiler l4, both boilers delivering steam to a main header I5. Each furnace is provided with the usual gas outlet duct or uptake l6 having a damper 18 ther in, both'uptakes being connected to av breeching I9 leading toa stack or other draft-inducing means (not shown). Beneath eachgrate 'H is a chamber 20 from which the air for combustion passes upwardly through the grate and the fuel bed. Air is admitted directly f-rom'theatmosphere into each chamberZU through'an open; ing 22 having a pivotally mounted door ordamper 23 associated therewith to control the flow of air. Both doors 23 are actuated by a comm-on shaft 24. Each chamber 20 is located rimme'diatelyanterior to the'fuel bed; in which-the initialcom busti'on of the fuel takes place. i 1 The air-admission doors 23 are controlled in accordance with the demand for heat from the furnaces. For this purpose I preferably utilize a suitable regulator 26 responsive to variations in the steam pressure in the header [5, this pressure being transmitted to the regulator through a pipe 2 1. The regulator is connected torthe shaft 24 by means of a link 28' and' an: arm 29.' This regulator 26 maybe of any suitable type, one satisfactorycon'struction being shown in the patent to Temple No. 2,049,549. 'It will be understood that upon a decrease -in the steam pressure in the header l5, the regulator '26wil1 turn the shaft 24 in such a'd'irection asto admit more air through the openings 22 and. thus .increase the rate of combustion. .z a

Each of the uptake dampers l8 iscontrolled in accordance with the pressure in the corresponding chamber 20 beneath the fuel bed, this pressure of course being slightly, below atmospheric. For this purpose each. damper i8 is provided with a shaft 3| having an arm- 32 thereon which is connected by a link 33 to the fluidactuated motor 35 of a regulator 36, this regulator being subjected to the pressure in the chamber 20 by means of a connecting pipe '31.- One suitable constniction for-the regulators 36 is disclosed in the patent to Temple No. 1,992,048.

' The operation of the invention will now be apparent from the'above disclosure. With :a bed of fuel burning on each ofthe grates II, the air for combustion will enter the chambers 20 through the openings 22 and pass upwardly through the fuel. The gaseous products of'combustionwill give up most of their heat to the boilers l4 and'then escape through the uptakes IE to the breeching 19. The steamgenerated in the boilers will pass into the header l5 and thence to a place of use. If the demand for steam should increase, the steam pressure will drop slightly and the regulator 26 will open the doors 23 to admit more air for combustion. Similarly, if the steam pres-sure should increase slightly the regulator will close the doors and decrease the flow of air. Each regulator 36 will control the corresponding uptake damper IS in such a way as to maintain a substantially constant pressure in the corresponding chamber 20 beneath the fuel bed. If this pressure should increase even in the slightest degree the regulator will open the uptake damper until the desired pressure is restored. Similarly a slight decrease in this pressure will result in closing the damper to restore the desired pressure. Such changes in the air pressure beneath the fuel bed may result from changes in the thickness or character of the fuel bed, from changes in the draft loss through the boiler caused by soot accumulations, from changes in the draft available at the uptake l6, or from movement of the air-admission doors 23. Whatever may be the cause of the pressure changes, each individual regulator 36 will control its particular damper l8 independently and maintain the desired pressure in the corresponding chamber 20 within very close limits. 7

It will be apparent that the rate of air flow into each furnace will depend upon the pressure in the chamber 20 and the position of the airadmission door 23. However the pressure in the chamber 20 is held constant, and by suitable adjustment of the regulators 36 both chambers 20 will be maintained'at the same pressure. Thus a substantially constant pressure differential will be maintained across each door 23, since the pressure'anteri'or to th'edoors is atmospheric. Furthermore, it is a simple matter to line up the two doors 23 on the shaft 24 so that they will'both be open to the same extent. Consequently the invention provides a method and apparatus whereby the air flow, and hence the combustion rate, may be equalized between the two furnaces despite varying fuel-bed thicknesses, unequal distribution of the draft, etc. Since the combustion rates are equalized there will be no tendency for one fuel bed to burn thin ahead ofthe other, and it will be a simple matter to keep both fuel beds in a uniform condition. y

Having thus. described my invention, what I claim as new and desire to secure by Letters Patent is; c c c 1. In combination with a fuel-burning fur nace having means to maintain a sub-atmospheric pressure at the. furnace outlet anda chamber into which air for combustion is drawn directly from the atmosphere. solely as a result of said sub-atmospheric pressure, the chamber being located immediately anterior to the zone of initial combustion, an air inlet damper to control the flow of air from the atmosphere into the chamber, a gas outlet damper at the furnace outlet, and a regulator arranged to consub-atmospheric pressure at the furnace outlet, a chamber located immediately anterior to the fuel bed into which air is drawn directly from the atmosphere solely as a result of said subatmospheric pressure, an air inlet damper to control the flow of air from the atmosphere into the chamber, a gas outlet damper at the furnace outlet, and a regulator arranged to control the gas outlet damper in accordance with the pressure in the chamber and to maintain said pressure substantially constant at a value slightly below atmospheric pressure, whereby a substantially constant pressure differential will be maintained across the inlet damper regardless of variations in fuel bed resistance.

3. The method of controlling combustion in a furnace having an air inlet damper and a gas outlet damper comprising the steps of maintrol the gas'outlet damper in accordance with the pressure in the chamber and to maintain said pressure substantially constant at a value slightly below atmospheric pressuregwhereby a substantially constant pressure differential 1 y will be maintained across the inlet damper.

2. In a combination with a fuel-burning furnace having a fuel bed, means to maintain a taining a sub-atmospheric pressure at the furnace outlet and thereby inducing a flow of air directly from the atmosphere and past the inlet damper-solely as a. result of said sub-atmospheric pressure, so regulating the outlet damper as to maintain the air pressure immediately anterior to the zone of initial combustion substantially constant at a value slightly below atmospheric pressure and thereby maintaining a substantially constant pressure differential across the inlet damper, and regulating the inlet damper to control the rate of combustion.

4. In combination with a'plurality of 'fuelburning furnaces, each furnace having a fuel bed, means to maintain a sub-atmospheric pressure at the outlet'of each furnace, achamber located immediately anterior' to each fuel bed into which air is drawn directly from the atmosphere solely as a result of saidsub-atmospheric pressure, an air inlet damper for each furnace to control the flow of air from the atmosphere into the corresponding chamber, a gas outlet damper at the outlet of each furnace, a regu lator for'each gas outlet damper arranged to control thesame in accordance with the pressure in the corresponding chamber and to maintain said pressure substantially constant at a value slightly below Fatmospheric pressure, whereby asubstantially-constant pressure differential will be maintained across each inlet damper regardless of variations in fuel-bed resistance, and a commonactuating means for all the air inlet dampers.

5.-The method of controlling combustion in a plurality offuel-burning furnaces each of which has an air inlet damper and a gas outlet damper comprising the steps 'of maintaining a sub-atmospheric pressure at each furnace outlet and thereby inducing a flOWof air directly from the atmosphere and past each inlet damper solely as a result of said sub-atmospheric pressure, so regulating each outlet damper as to maintain the airpressure immediately anterior to the zone of initial-combustion in the corresponding furnace; substantially constant at a value slightly below atmospheric pressure and thereby maintaining a substantially-constant pressure differential across each" inletdamper, and regulating all the inlet dampers simultaneously to control the rate of combustion in all the furnaces.

. JOHN J. KLINKER. 

